1. FIELD OF THE INVENTION
The present invention relates in general to an improved double acting actuator which is widely used in hydraulic power transmissions which are required to move accurately, such as a transfer machine, an automatic stock feed, etc., and, in particular, to a new and useful type of an actuator of which a piston rod can reciprocate in the cylinder in opposite axial directions and can rotate, relative to the cylinder, in opposite angular directions, and further, an accurate positioning of the piston rod can be effected at a beginning and/or an end of operation movements thereof.